1use core::{
2 cell::Cell,
3 sync::atomic::{AtomicUsize, Ordering::SeqCst},
4};
5
6use once_cell::unsync::OnceCell;
7
8#[test]
9fn once_cell() {
10 let c = OnceCell::new();
11 assert!(c.get().is_none());
12 c.get_or_init(|| 92);
13 assert_eq!(c.get(), Some(&92));
14
15 c.get_or_init(|| panic!("Kabom!"));
16 assert_eq!(c.get(), Some(&92));
17}
18
19#[test]
20fn once_cell_with_value() {
21 const CELL: OnceCell<i32> = OnceCell::with_value(12);
22 let cell = CELL;
23 assert_eq!(cell.get(), Some(&12));
24}
25
26#[test]
27fn once_cell_get_mut() {
28 let mut c = OnceCell::new();
29 assert!(c.get_mut().is_none());
30 c.set(90).unwrap();
31 *c.get_mut().unwrap() += 2;
32 assert_eq!(c.get_mut(), Some(&mut 92));
33}
34
35#[test]
36fn once_cell_drop() {
37 static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
38 struct Dropper;
39 impl Drop for Dropper {
40 fn drop(&mut self) {
41 DROP_CNT.fetch_add(1, SeqCst);
42 }
43 }
44
45 let x = OnceCell::new();
46 x.get_or_init(|| Dropper);
47 assert_eq!(DROP_CNT.load(SeqCst), 0);
48 drop(x);
49 assert_eq!(DROP_CNT.load(SeqCst), 1);
50}
51
52#[test]
53fn once_cell_drop_empty() {
54 let x = OnceCell::<String>::new();
55 drop(x);
56}
57
58#[test]
59fn clone() {
60 let s = OnceCell::new();
61 let c = s.clone();
62 assert!(c.get().is_none());
63
64 s.set("hello".to_string()).unwrap();
65 let c = s.clone();
66 assert_eq!(c.get().map(String::as_str), Some("hello"));
67}
68
69#[test]
70fn get_or_try_init() {
71 let cell: OnceCell<String> = OnceCell::new();
72 assert!(cell.get().is_none());
73
74 let res = std::panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
75 assert!(res.is_err());
76 assert!(cell.get().is_none());
77
78 assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
79
80 assert_eq!(cell.get_or_try_init(|| Ok::<_, ()>("hello".to_string())), Ok(&"hello".to_string()));
81 assert_eq!(cell.get(), Some(&"hello".to_string()));
82}
83
84#[test]
85fn from_impl() {
86 assert_eq!(OnceCell::from("value").get(), Some(&"value"));
87 assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
88}
89
90#[test]
91fn partialeq_impl() {
92 assert!(OnceCell::from("value") == OnceCell::from("value"));
93 assert!(OnceCell::from("foo") != OnceCell::from("bar"));
94
95 assert!(OnceCell::<String>::new() == OnceCell::new());
96 assert!(OnceCell::<String>::new() != OnceCell::from("value".to_owned()));
97}
98
99#[test]
100fn into_inner() {
101 let cell: OnceCell<String> = OnceCell::new();
102 assert_eq!(cell.into_inner(), None);
103 let cell = OnceCell::new();
104 cell.set("hello".to_string()).unwrap();
105 assert_eq!(cell.into_inner(), Some("hello".to_string()));
106}
107
108#[test]
109fn debug_impl() {
110 let cell = OnceCell::new();
111 assert_eq!(format!("{:#?}", cell), "OnceCell(Uninit)");
112 cell.set(vec!["hello", "world"]).unwrap();
113 assert_eq!(
114 format!("{:#?}", cell),
115 r#"OnceCell(
116 [
117 "hello",
118 "world",
119 ],
120)"#
121 );
122}
123
124#[test]
125#[should_panic(expected = "reentrant init")]
126fn reentrant_init() {
127 let x: OnceCell<Box<i32>> = OnceCell::new();
128 let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
129 x.get_or_init(|| {
130 let r = x.get_or_init(|| Box::new(92));
131 dangling_ref.set(Some(r));
132 Box::new(62)
133 });
134 eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
135}
136
137#[test]
138fn aliasing_in_get() {
139 let x = OnceCell::new();
140 x.set(42).unwrap();
141 let at_x = x.get().unwrap(); // --- (shared) borrow of inner `Option<T>` --+
142 let _ = x.set(27); // <-- temporary (unique) borrow of inner `Option<T>` |
143 println!("{}", at_x); // <------- up until here ---------------------------+
144}
145
146#[test]
147// https://github.com/rust-lang/rust/issues/34761#issuecomment-256320669
148fn arrrrrrrrrrrrrrrrrrrrrr() {
149 let cell = OnceCell::new();
150 {
151 let s = String::new();
152 cell.set(&s).unwrap();
153 }
154}
155